Microscope objective

ABSTRACT

The present invention relates to microscope objectives and more particularly, to a high-magnification microscope objective with a magnification 100 and numerical aperture 0.9. Besides, for the microscope objective according to the present invention, aberrations, especially spherical and chromatic aberrations are favourably corrected by selecting the sum of powers at all lens surfaces in the lens system, i.e., Sigma (ni 1 - ni)/ri, as a positive value with a small absolute value.

United Stat 1111 3,822,931- Matsubara July 9, 1974 [54] MICROSCOPE OBJECTIVE FOREIGN PATENTS OR APPLICATIONS lnventorl Masaki Mfltsubal'fl, Tokyo, Japan 27,850 9/1970 Japan 350/175 ML [73] Assignee: Olympus Optical Co., Ltd.,

Tokyo-to, Japan Primary Examiner-J0hn K. Corbin [22] Filed May 23 1973 Attorney, Agent, or Firm-Cushman, Darby &

Cushman [21] Appl. No.: 363,277

57 ABSTRACT [30] Foreign Application Priority Data 1 i Ma 27 1972 M an 4762799 The present 1nvent1on relates to m1croscope ObjCCIlVCS y p f and more particularly, to a high-magnification microscope objective with a magnification 100 and numeri- [52] Cl 350/215 350/175 g cal aperture 0.9. Besides, for the microscope objective according to the present invention, aberrations, espe- S cially spherical and chromatic aberrations are favourao bly corrected by selecting the sum of powers at all lens surfaces in the lens system, i.e., 201 ni)/r, as a [56] uNlTE g gzz lzs ggrENTs positive value with a small absolute value. 3,661,446 5/1972 MOri et al. 350/177 x 1 Claim, 4 Drawingfigures PAIENIEDJUL 9l974 FIG. I

OS C

SPHERICAL ABERRATION ASTIGMATISM F.A.I8

F d c NAOS -.A.o.9

I I I I I I I I I I I I -I6 0 lb 0 d FIG. 2b

-I O I FIG. 2c

FIG. 20

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microscope objective with a flat field, high magnification and large numerical aperture.

2. Description of the Prior Art Though a microscope objective with the magnification 80 is already provided, design of a microscope objective of still higher magnification has been looked for. Even if, however, the magnification of the conventional objective with the magnification 80 is simply increased by proportionally enlarging as it is, spherical aberration deteriorates because of the extremely high magnification and, moreover, chromatic aberration also becomes very unfavourable. Therefore, such objective cannot be put to practical use. To provide a high-magnification microscope objective with the high magnification of I00, adequate improvement is essential.

SUMMARY OF THE INVENTION It is, therefore, a principal object of the present invention to provide a microscope objective with a magnification I and numerical aperture 0.9 for which aberrations, especially spherical and chromatic aberrations, are quite favourably corrected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows a sectional view illustrating the composition of the embodiment of the microscope objective according to the present invention; and

FIG. 2A, FIG. 2B, and FIG. 2C show graphs illustrating aberration curves of the embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1, the microscope objective according to the present invention comprises six lenses or components. The first lens L second lens L and third lens L are positive meniscus lenses with their concave surfaces respectively positioned on the object side. The fourth lens component L is a cemented positive triplet, the fifth lens L is a biconvex lens and the sixth lens L is a negative meniscus lens arranged leaving a large airspace from said fifth lens L Besides, the microscope objective according to the present invention has numerical data as given below.

In the above numerical data, reference symbol f represents the total focal length of the lens system as a whole, reference symbol [3 represents the magnification of the lens system as a whole, reference symbols r, through r represent radii of curvature of respective lens surfaces, reference symbols d, through d represent thicknesses of respective lenses and spaces between lenses, reference symbols n through u represent refractive indexes of respective lenses for the d-line, reference symbols v, through 1/ represent Abbe's numbers of respective lenses for the d-line, and reference symbol W.D. represents the work distance.

For the microscope objective according to the present invention having numerical data as given in the above table, the algebraic sum of powers of respective lens surface, i.e., 201 n,-)/r,, is a positive value with a small absolute value and, therefore, spherical aberration of this objective is favourably corrected. Besides, Petzvals sum is made small by making powers of respective lens surfaces as positive values. The airspace (1, between the fifth lens L and the sixth lens L is made larger than the sum of the thickness d, of the first lens L, and thickness d of the sixth lens L i.e., d, d By these arrangements, curvature of the field is satisfactorily corrected and the field is made flat. Furthermore, chromatic aberration is favourably corrected by making both Abbes number 1/ of the second lens L and Abbe's number 1/, of the sixth lens L as 81.8. At the same time, over-correction of lateral chromatic aberration, which occurs by the fact that a material of Abbes number 11 81.8 is used for the second lens L is favourably corrected by using the material of Abbes number v 81.8 also for the sixth lens L Besides, chromatic aberration and other aberrations are favourably balanced by using a cemented positive triplet as the fourth lens component L, and by making Abbes number 11 of the middle lens of said cemented lens component as 37.5.

As explained in the above, the microscope objective of the present invention has a high magnification of I00 and large numerical aperture, and aberrations of said microscope objective, expecially, spherical and chromatic aberrations are quite favourably corrected as it is evident also from aberration curves shown in FIG. 2A, FIG. 2B, and FIG. 2C.

I claim:

I. A microscope objective comprising first, second, third, fourth, fifth and sixth lens components, wherein said first said second and said third are positive meniscus lenses having their concave surfaces respectively positioned on the object side, said fourth is a cemented positive triplet component, said fifth is a biconvex lens and said sixth is a negative meniscus lens arranged by leaving a large airspace from said fifth lens and having the convex surface positioned on the objective side, r l9900 and said microscope objective having numerical data as dn=l "1:1 "F951 given below: r,,=l9.900

d.,=7.96 5 r =8.6l9

d 5.05 n L486 v =8l.8 -2.09 F a 1.26? r =3.8O2

d,=l.89 n =l.5l6 11 54.2

08 I 6 d 1:007 where reference symbol f represents the total focal m=' d 8 486 8 length of the lens system as a whole, reference symr bols r, through r represent radii of curvature of 870 41:01) respective lens surfaces, reference symbols d V'-'-- 45:1) VJ=95 2 through d represent thlcknesses of respective 16:0 12 lenses and spaces between lenses, reference symr,=i4.0s4 A I 5 bols n through n represent refractive indexes of r 054 dr=l93 "F1434 "F952 respective lenses for the d-line and reference symd..=0.64 n =l.834 v =37.2 bols 1/, through represent Abbes numbers of re- 35 n 434 v 2 spective lenses for the d-line.

v n- F -sssu 

1. A microscope objective comprising first, second, third, fourth, fifth and sixth lens components, wherein said first said second and said third are positive meniscus lenses having their concave surfaces respectively positioned on the object side, said fourth is a cemented positive triplet component, said fifth is a biconvex lens and said sixth is a negative meniscus lens arranged by leaving a large airspace from said fifth lens and having the convex surface positioned on the objective side, and said microscope objective having numerical data as given below: 